This invention relates to seal devices for large vessels and other containers and, more particularly, to large area seals for attaching to a ferromagnetic structure.
It is well known that significant environmental damage can occur from the leakage of liquids stored in large containers, such as tankers and bulk carrier vessels and shore-based tanks. The breach of a supertanker hull, e.g., the EXXON Valdez disaster, can result in the release of millions of gallons of petroleum to an ecologically sensitive system or can contribute to the general pollution of waterways. In chemical storage areas located on shore, leaks can be contained about a storage vessel, but the chemicals might be absorbed in earth surrounding the containment area for subsequent migration to water supplies or might be released if the containment area is flooded, e.g., as occurred during the recent flooding of the Mississippi River system.
In all instances, the preferred corrective action is to stop the leak as soon as possible. Various devices have been developed for forming temporary patches over the area of the leak until a permanent patch can be made. Such devices include inflatable bladders, foam blankets, etc., that are mechanically held against the leak. Magnetic attachment offers many advantages for securing a temporary seal about a leak through a container of ferromagnetic material since the magnet is attracted directly to the surface for securing the seal to the surface. Some devices have used electromagnets to hold the patch to the surface of the leaking container. However, the use of electromagnets depends on the availability of electrical power and can be difficult to use in certain environments, e.g., underwater or explosive atmospheres.
In some applications, e.g., a leak in a tanker hull, the seal must remain in place as the container is moved. The drag forces induced as a ship moves through water can be substantial and any seal device must accommodate those forces in order to maintain the seal during movement.
Accordingly, it is an object of the present invention to provide a seal device that is attachable to a ferromagnetic surface using permanent magnets.
Another object of the present invention is to provide a seal device using permanent magnets having an attractive force on a ferromagnetic material that can be varied from a low level for seal placement about the leak and a high level for exerting a force about the periphery of the leak.
Yet another object of the present invention is to provide a seal device that will remain stationary above a leak if the container is moving, e.g., a ship hull during movement through water.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.